1. Field of Invention
The present invention relates to a secondary battery and a manufacturing method of the same. More particularly, the present invention relates to a battery core and a manufacturing method of the same.
2. Description of Related Art
A secondary battery is a battery which can be recharged. There are various types of secondary batteries that vary in structural design or in material utilized therein. It is not advisable to charge a primary battery due to the risk of explosion of the battery. Some secondary batteries may be damaged by reverse charging as a result of being totally discharged, while some secondary batteries have to be totally discharged periodically. Today, secondary batteries are widely used in various kinds of electrical devices with low power requirements, such as car starters, mobile apparatuses, uninterruptible power supplies, etc. Moreover, the requirements of low cost and weight, and increased lifetime of secondary batteries used in hybrid vehicles and electric vehicles have been such that the technology of this field continues to improve.
In recent years, secondary batteries have been widely used as the power source in mobile electrical apparatuses. Among the different types of secondary batteries, the demand for lithium secondary batteries has been steadily increasing due to their characteristics of high energy density, high discharge voltage, and good power output stability.
A secondary battery usually includes a plurality of battery cores connected in series to satisfy the voltage and power requirements of various devices. In addition, because of the charge-discharge characteristics of the secondary battery and the fact that there are differences between the battery cores, an electrical balancing control of each battery core in the secondary battery is needed, so as to avoid overcharging or overdischarging of the battery cores which may cause early failure of the secondary battery.